7.3.1 INTRODUCTION

7.3.1 INTRODUCTION

Exterior Gateway Protocols are utilized for inter-Autonomous System
routing to exchange reachability information for a set of networks
internal to a particular autonomous system to a neighboring
autonomous system.

The area of inter-AS routing is a current topic of research inside
the Internet Engineering Task Force. The Exterior Gateway Protocol
(EGP) described in Section [Appendix F.1] has traditionally been the
inter-AS protocol of choice, but is now historical. The Border
Gateway Protocol (BGP) eliminates many of the restrictions and
limitations of EGP, and is therefore growing rapidly in popularity.
A router is not required to implement any inter-AS routing protocol.
However, if a router does implement EGP it also MUST IMPLEMENT BGP.
Although it was not designed as an exterior gateway protocol, RIP
(described in Section [7.2.4]) is sometimes used for inter-AS
routing.